Her Anaphylactic Episodes Weren't Allergies — They Were a Rare Disease She'd Never Heard Of

Kristine used to have anaphylactic episodes that came out of nowhere. Sudden, terrifying, full-body reactions with no explanation. Doctors kept looking for an allergy — a food, an environmental trigger, something — but nothing turned up. It wasn’t until she received a diagnosis of indolent systemic mastocytosis, or ISM, that the pieces finally fit together.

ISM is a rare disease that most people have never heard of. About one in 5000 adults are living with systemic mastocytosis. For those who get a diagnosis, it can be life-changing.

Not an Allergy — A Mast Cell Problem

One of the most important things to understand about ISM is that it isn’t an allergy, even though it can look exactly like one.

Everyone has mast cells. They’re a normal part of the immune system: white blood cells that store chemicals like histamine and prostaglandin and release them when the body senses a threat. In most people, that process works as it should.

But people with ISM have too many abnormal mast cells. When triggered – by food, stress, temperature changes, or even exercise – the excess mast cells dump those stored chemicals into the system. That sudden release is what drives symptoms. For Kristine, it was serious enough to cause anaphylaxis, a life-threatening reaction. For others, ISM can show up as skin reactions, digestive issues, fatigue, brain fog, or bone pain. Symptoms vary widely from person to person and can be unpredictable day to day.

In about 95% of cases, ISM is caused by a mutation in the KIT gene — a small change in DNA can lead to uncontrolled growth of abnormal mast cells throughout the body.

Learning to Navigate Life With ISM

A diagnosis gives a name to what’s happening, but it doesn’t make daily life easier. Kristine has had to make real adjustments to how she lives — avoiding certain foods that aren’t safe, giving up activities she once enjoyed, and constantly accounting for what might trigger her mast cells.

That kind of ongoing navigation is common among people with ISM. The disease can affect many areas of the body and disrupt work, routine, and quality of life in ways that aren’t always visible to others. Because ISM is rare and often misunderstood, many people go years without a proper diagnosis, often trying to manage symptoms without understanding the root cause. 

Why Talking to Your Doctor Matters

If you experience unexplained allergic-type reactions, recurring symptoms without a clear cause, or have already been diagnosed and still have questions — talking to your doctor is an important next step.

ISM may be more common than previously thought, and the right diagnosis opens the door to real options. There are ways to manage ISM and help reduce symptoms, but the path forward starts with identifying what type of SM you have and working with a knowledgeable care team to find an approach that fits your situation.

Find Support and Information

MastoConnect is a resource built for people living with systemic mastocytosis and those who care for them. The site covers what SM is, what a diagnosis means, how it can be managed, and how to connect with a community of people navigating the same challenges.

If you or someone you love is living with ISM, you don’t have to figure it out alone.

 

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